Based on the methodology used, PT may reduce tissue breakdown resulting from PD in unstressed rats. The protocol used for restraint stress influenced the immunomodulatory effects of PT in intestinal and periodontal tissues.

The aim of this article was to evaluate the in vivo mechanism of action through which ractopamine reduces the amount of adipose tissue in carcass of animals fed diets supplemented with this drug. Literature search was carried out, using the keywords Ractopamine, lipogenesis, lipolysis, fatty acid and adipose tissue. The scoring system was designed for the adequacy of the methodology. A total of eight papers were found-all published in the English language. The determination of lipolysis and lipogenesis was carried out using different methods-from the quantification of non-esterified fatty acids in the blood to molecular analyses of adipose tissue. The review analysis suggested that, at least in the pigs, the use of this drug reduced lipid deposition in the carcass due to a greater inhibition of lipogenesis than an increase in lipolysis.

-The objective of this study was to evaluate the effect of photoperiod on locomotor activity, growth and gonadal development in Nile tilapia (Oreochromis niloticus) fingerlings. A completely randomised design was used, with five treatments (0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D) and four replicates, with the aquarium as the experimental unit. One hundred and sixty fingerlings of tilapia weighing 3.21±0.05 g and measuring 4.35±0.07 cm each were distributed among 20 aquaria of 20 L in a recirculation system with the temperature controlled to 27 °C, with eight fish per aquarium. Feeding was carried out twice daily for 75 days, with extruded feed containing 40% crude protein. The fingerlings subjected to a photoperiod of 12L:12D as well as those under 18L:6D and 24L:0D showed the greatest locomotor activity, whereas those under 6L:18D and 0L:24D showed the lowest activity. Fish subjected to a photoperiod of 18L:6D and 24L:0D showed the highest levels of performance. However, manipulation of the photoperiod did not influence the gonadal development, survival or the appearance of deformities in juvenile Nile tilapia. Under long photoperiods (18L:6D and 24L:0D), fish direct their energy to somatic growth and induce best feed efficiency.

RESUMO.O presente trabalho objetivou avaliar o uso de ractopamina em diferentes níveis de inclusão na dieta para suínos em terminação. Foram utilizados 50 suínos híbridos comerciais com peso inicial de 74,08 (1,42) kg, aleatoriamente distribuídos em cinco blocos casualizados. Havia dois animais em cada parcela experimental, macho e fêmea, alimentados com dieta suplementada com ractopamina (0, 5, 10, 15 e 20 ppm) durante 28 dias. Foram avaliados desempenho e características de carcaça dos animais. A ractopamina melhorou o desempenho, espessura de toucinho, profundidade, área de olho de lombo e rendimento de carne na carcaça, porém sem influenciar no consumo de ração, rendimento de cortes e qualidade da barriga. Exceto a dose de 0 ppm, não houve diferença entre as doses de ractopamina utilizadas. O modelo de regressão Linear Response Plateau, aplicado nas variáveis onde houve significância, estimou o ponto ótimo de suplementação deste aditivo entre 4,09 a 5,14 ppm. Houve aumento de 6,09% no índice de bonificação quando foi utilizado o nível de 5 ppm de ractopamina. Conclui-se que a ractopamina é eficaz em melhorar o desempenho e as características de carcaça de suínos em terminação.Palavras-chave: agonista β-adrenérgico, carcaça, desempenho, partidor de nutrientes, qualidade de carne.ABSTRACT. Ractopamine hidrochloride in diets for finishing pigs. The present work was carried out to evaluate different inclusion levels of ractopamine in diets for finishing pigs. Fifty animals with initial weight of 74.08 (1.42) kg selected for high meat deposition were used, randomly allotted in five blocks. Each experimental unit had two animals, barrow and gilt, fed diets with ractopamine (0, 5, 10, 15 and 20 ppm) for 28 days. Growth performance and carcass characteristics were evaluated. Ractopamine improved final weight, average daily gain, feed:gain ratio, backfat thickness, loin depth, loin eye area and lean tissue yield, but did not influence feed intake, cut yields and belly quality. No differences were found among the doses of ractopamine utilized. The optimum level of supplementation of this additive, as estimated by the Linear Response Plateau regression model, was between 4.09 and 5.14 ppm. There was an average increase of 6.09% in the bonus index when ractopamine was used. It was concluded that ractopamine is efficient in increasing the performance and carcass characteristics of finishing pigs.

Materials and methods Experimental procedureAll animals were cared for in accordance with the principles promulgated by ethical guidelines and the experimental protocol was approved by the Ethics Committee in Animal Experimentation of the Federal University of Lavras.Forty commercial crossbred pigs (TOPIGS) from the Swine Experimental Centre of the Animal Science Department, Federal University of Lavras, barrows and Abstract: Ractopamine (RAC) causes fat deposition and/or fatty acid synthesis reduction and increases the rate of protein synthesis and muscle growth. However, there are few scientific studies detailing the mechanism of action of RAC and its possible metabolic pathways in swine. The objective of this study was to evaluate the effect of RAC on lipid metabolism of finishing pigs. Subcutaneous and retroperitoneal fat, muscle, and blood samples were collected at slaughter. Forty pigs were fed different RAC levels (ppm): 0, 5, 10, 15, and 20. RAC did not affect lipoprotein lipase activity in any of the tissues. There were no changes in insulin levels, but a linear increase in serum triacylglycerol, total cholesterol, and HDL-cholesterol (HDL-c) was seen. The insulin-dependent glucose transport (GLUT4) and fatty acid synthase amounts present in animals' adipose tissue did not differ, but the muscle GLUT4 presented a negative quadratic effect. The smallest GLUT4 amount (0.959) was estimated for 15.5 ppm of RAC. Serum glucose increased linearly, while a linear decrease in glycogen content was detected. The results indicate that RAC acts upon lipid metabolism in order to stimulate lipolysis, while there are changes in carbohydrate metabolism that might support lean growth in these animals.